Field of the Disclosure
The present disclosure relates to an OFDM encoding apparatus and a corresponding OFDM encoding method for encoding OFDM symbols into an OFDM signal. Further, the present disclosure relates to a transmitting apparatus and a corresponding transmitting method. Still further, the present disclosure relates to a computer program and a non-transitory computer-readable recording medium.
Description of Related Art
Many different systems, like systems in accordance with ATSC 3.0, DVB-T2, DOCSIS 3.1 or the DVB second generation cable transmission standard (DVB-C2; e.g. described in ETSI EN 302769 V1.1.1 (2010 April)), use OFDM (Orthogonal Frequency Division Multiplex) for the transmission of payload data. While OFDM has many advantages, it has the disadvantage that the resulting OFDM signal (in the frequency domain) has rather high shoulders at the edge of the spectrum. Conventionally, filtering is applied after the OFDM generation to reduce the effects onto neighboring channels. This is especially important for OFDM systems that deploy high QAM modulations (e.g. DVB-C2 using up to 4096-QAM), which requires very high signal-to-noise ratios and thus high signal levels. However, steep filters applied after the OFDM generation reduce the signal quality of the OFDM signal in several ways. The impulse response of the filter introduces inter symbol interference and consumes part of the available Guard Interval. In case of DVB-C2 with Guard Interval 1/128, the overall Guard Interval length is only 32 samples, which does not allow for long filters. Furthermore, the passband ripple of the filter (in the frequency domain) deteriorates the OFDM subcarriers.
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventor(s), to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present disclosure.